Brush off the potatoes, wash them and cook for about 15 minutes. Drain, quench, possibly peel and then let cool.
In the meantime, stir the sour cream with the quark until smooth, add the garlic and herbs and season with salt and pepper. Refrigerate.
Squeeze out the soaked bread roll and chop it up well. Knead well with the minced meat, onions, marjoram, mustard, paprika powder and salt and pepper in a bowl. If necessary, season again. Shape the minced dough into 16 small balls.
Cut the zucchini into thick slices, wash the tomatoes. Then stick the meatballs with the potatoes, zucchini and tomatoes on skewers.
Grill on the grill for about 15 minutes. Season with salt and pepper and serve with the herb dip.